public void GetById_GivesActivity()
{
int activityId = 1;
_activityRepository.Setup(a => a.GetById(activityId)).Returns(_dummyDBContext.Activity1);
ActionResult <Activity> actionResult = _controller.GetById(activityId);
var response = actionResult?.Result as OkObjectResult;
Activity activityThatCameBackFromResponse = response?.Value as Activity;
Assert.Equal("Testatelier", activityThatCameBackFromResponse.Name);
}